Gas valve control system for a water heater

ABSTRACT

A system and method of operating a gas fuel valve control circuit are disclosed. The gas valve control circuit includes a gas valve assembly configured to control a flow of a fuel gas to a load and a switch assembly including a switch in each leg of a plurality of legs of a power supply to the gas valve assembly. The switch assembly is configured to supply power and a return to the gas valve assembly in a first position and to open the plurality of legs of the power supply to the gas valve assembly in a second position. The switch assembly is configured to indicate a position of the switch assembly.

FIELD

This disclosure relates generally to water heater gas valve controlcircuits, and, more particularly, to a gas valve control circuit havinga switch that provides a gas valve switch indication to a controller.

BACKGROUND

Water heaters typically include a manual gas shut off valve or anelectrical switch that disconnects the gas valve from electrical power.Powered vent water heaters have typically used a master on/off switch toswitch all power to the appliance off. If the valve has a system levelswitch that effectively stops operation of the water heater when off anddisconnects power from the gas valve coil, the original equipmentmanufacturer (OEM) can eliminate the master switch from their assembly.Powered vent water heaters have a large inductive fan load, for exampleabout 2 amps at 120 volts, due to the powered draft inducer. If a gasvalve switch only switches the gas valve off and the control systemremains energized, the control system may indicate errors to an operatorwhen the control system attempts to light-off the water heater. Thiswould be confusing to the operator who, by the position of the gas valveswitch, thinks the water heater is shutdown. An improved control systemis needed.

This background section is intended to introduce the reader to variousaspects of art that may be related to the present disclosure, which aredescribed and/or claimed below. This discussion is believed to behelpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentdisclosure. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

BRIEF DESCRIPTION

In one aspect, a gas valve control circuit includes a gas valve assemblyfor controlling a flow of a fuel gas to a load and a switch assembly.The switch assembly supplies power and a return to the gas valveassembly in a first position and opens the plurality of legs of thepower supply to the gas valve assembly in a second position. The switchassembly indicates a position of the switch assembly.

In another aspect, a method of operating a gas fuel valve control systemincludes sensing, by a controller, a position signal of a gas fuel valveswitch that includes a first component having a first electricalcharacteristic and a second component having a second electricalcharacteristic when the gas fuel valve switch is in an open positionwherein the second electrical characteristic being different than thefirst electrical characteristic, the gas fuel valve switch maintaining apower supply leg and a power return leg open when the gas fuel valveswitch is in the open position. The method also includes sensing, by thecontroller, the position signal of the gas fuel valve switch thatincludes only the first component when the gas fuel valve switch is in aclosed position. The gas fuel valve switch maintains the power supplyleg and the power return leg closed when the gas fuel valve switch is inthe closed position. The method further includes operating the gas fuelvalve control system using the sensed position of the gas fuel valveswitch.

In yet another aspect, a powered vent electronic control circuitincludes a controller configured to control an operation of heatingdevice having a powered draft inducer, a gas valve assembly configuredto control a flow of a fuel gas to a burner of a heating device, and aswitch assembly that includes a switch in each leg of a plurality oflegs of a power supply to the gas valve assembly. The switch assembly isconfigured to supply power and a return to the gas valve assembly in afirst position and to open the plurality of legs of the power supply tothe gas valve assembly in a second position, the switch assembly isconfigured to indicate a position of the switch assembly to thecontroller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a powered vent electronic controlcircuit in accordance with an example embodiment of the presentdisclosure.

FIG. 2 is a flowchart of an example method of operating a gas fuel valvecontrol system in accordance with an example embodiment of the presentdisclosure.

Although specific features of various embodiments may be shown in somedrawings and not in others, this is for convenience only. Any feature ofany drawing may be referenced and/or claimed in combination with anyfeature of any other drawing.

Unless otherwise indicated, the drawings provided herein are meant toillustrate features of embodiments of the disclosure. These features arebelieved to be applicable in a wide variety of systems comprising one ormore embodiments of the disclosure. As such, the drawings are not meantto include all conventional features known by those of ordinary skill inthe art to be required for the practice of the embodiments disclosedherein.

DETAILED DESCRIPTION

The following detailed description illustrates embodiments of thedisclosure by way of example and not by way of limitation. It iscontemplated that the disclosure has general application to fuel gasvalve control systems in industrial, commercial, and residentialapplications.

At least some known control systems use a relatively low power waterheater valve for powered vent controls. Mains power is stepped down viaa transformer to a lower voltage for loads, such as, but not limited tospark ignition, relay coils, logic, and gas valve coils. This allows theuse of a low cost switch because the loads being switched are small andlow voltage. However, this solution also requires a large expensivetransformer to step down voltage to these loads, at least partiallynegating the savings realized by the low cost switch. Generating sparkand flame sense voltage from the lower voltage is more expensive thenpowering them directly from mains voltage.

Embodiments of an improved fuel gas valve control system are describedherein. In one embodiment, the fuel gas valve control system uses adouble-pole double-throw (DPDT) manually-operated switch in the lowestcost location, such that its only load is the gas valve coil. It usesone of the “off” contacts to supply a low current DC voltage to the gasvalve sense circuit. This allows the controller to sense the position ofthe switch using existing circuits for gas valve sense (Gas ValveNormally Open relay contact check). If the switch is turned off whenthere is no call for heat, the controller senses a DC voltage at a gasvalve normally open (GVNO) terminal and prevents a call for heat and allindications of operation (LEDs etc.). If the gas valve switch is turnedoff during a call for heat, the gas valve will turn off, the controlwill sense a flame loss, turn off the GV relay, and try to re-light theburner. When the GV relay turns off, the control will see DC voltage andprevent a call for heat and all indications of operation (LEDs etc.).

The following description refers to the accompanying drawings, in which,in the absence of a contrary representation, the same numbers indifferent drawings represent similar elements.

FIG. 1 is a schematic block diagram of a powered vent electronic controlcircuit 100 in accordance with an example embodiment of the presentdisclosure. In the example embodiment, a controller 102 is configured tocontrol an operation of heating device 104 such as, but not limited to ahot water heater. Heating device 104 includes, for example, a combustionchamber 106 for combusting a fuel, for example, a fuel gas, such as, butnot limited to natural gas. The fuel gas is introduced into combustionchamber 106 through a burner 108 from a source of fuel gas 110. A flowof the fuel gas is controlled by a gas valve assembly 112. A fuel gasmanual shutoff valve 113 is provided to isolate fuel from heating device104.

Heating device 104 also includes a powered draft inducer 114, whichincludes a fan 116 and a prime mover, such as, but not limited to anelectric motor 118 coupled together via a shaft 120. Fan 116 is coupledin flow communication with combustion chamber 106 to permit purging ofcombustion chamber 106 and exhausting of combustion gases generatedduring operation of heating device 104.

Heating device 104 further includes a plurality of sensors, whichprovide information to controller 102, typically in the form ofelectrical signals or electromagnetic signals received from the sensors.For example, a flame sensor 122 may be positioned within combustionchamber 106 to detect a flame 124 emanating from burner 108. In anotherexample embodiment, a flame sensor 126 may be positioned outside ofcombustion chamber 106 with access to combustion chamber 106 through aviewing port 128. A pressure switch 130 is coupled in flow communicationwith combustion chamber 106 and configured to sense a pressure withincombustion chamber 106.

Powered vent electronic control circuit 100 includes a switch assembly132 that includes a first double-throw switch 134 and a seconddouble-throw switch 136 in respective legs 138, 140 of a power supplycircuit 142 to gas valve assembly 112. In the example embodiment, powersupply circuit 142 includes a full wave bridge rectifier 144. In otherembodiments, power supply circuit 142 may include other components tofacilitate supplying electrical power from switch assembly 132 to gasvalve assembly 112.

Switch assembly 132 is configured to supply power and a return to gasvalve assembly 112 in a first position (shown in solid lines in FIG. 1)and to open the plurality of legs of power supply circuit 142 to gasvalve assembly 112 in a second position (shown in dotted lines in FIG.1). Switch assembly 132 includes first double-throw switch 134configured to supply power to gas valve assembly 112 in the firstposition and to inject a switch assembly position signal 146 tocontroller 102 in a second position. Switch assembly 132 also includessecond double-throw switch 136 configured to connect a return path 148to gas valve assembly 112 in the first position and to open the returnpath from the gas valve in the second position.

A first important feature of switch assembly 132 is that it supplieselectrical power only to only gas valve assembly 112, which permits useof a lighter duty and less expensive switch because of the lighterelectrical load of only gas valve assembly 112. Another importantfeature of switch assembly 132 is that it provides an indication of itsposition to controller 102. Because switch assembly 132 is typicallyembodied in a manually-operated, two-position switch, without switchassembly 132 indicating its position to controller 102, switch assembly132 could be opened, removing power from gas valve assembly 112.Controller 102 would then detect errant operation of heating device 104without a known or discernible cause. This could put powered ventelectronic control circuit 100 in an in determinant state, from which itwould not be able to generate proper outputs.

In the example embodiment, controller 102 is configured to sense a gasvalve position signal 150 having only an only an alternating current(AC) component when the switch assembly is in the first position. The ACcomponent is supplied by an input power supply line 152 to switchassembly 132. Controller 102 is also configured to sense a gas valveposition signal having an AC component and a direct current (DC)component when the switch assembly is in the first position.

Powered vent electronic control circuit 100 also includes a gas valverelay 154 and an inducer fan relay 156. Each of gas valve relay 154 andinducer fan relay 156 are controlled by controller 102 throughrespective control lines 158, 160. Contacts of gas valve relay 154 andinducer fan relay 156 are coupled serially between a mains power supply162 for powered vent electronic control circuit 100 and switch assembly132.

Powered vent electronic control circuit 100 also includes a sparkignition circuit 164 and a flame sensing circuit 166, which are bothcontrolled by controller 102 through respective control lines 168, 170.

Powered vent electronic control circuit 100 also includes a parameterset point input device 172 and a parameter sensor 174 configured toprovide inputs to controller 102. In the example embodiment, atemperature set point is selectable through parameter set point inputdevice 172 and parameter sensor 174 is embodied as a temperature sensor.In the example embodiment, when parameter sensor 174 senses atemperature less than a set point temperature, controller 102 generatesthe appropriate signals to operate heating device 104.

FIG. 2 is a flowchart of an example method 200 of operating a gas fuelvalve control system in accordance with an example embodiment of thepresent disclosure. In the example embodiment, method 200 includessensing 202, by a controller, a position signal of a gas fuel valveswitch that includes a first component having a first electricalcharacteristic and a second component having a second electricalcharacteristic when the gas fuel valve switch is in an open position.Typically, the second electrical characteristic is different than thefirst electrical characteristic. For example, in an embodiment, thefirst electrical characteristic may be a frequency of the firstcomponent. A signal having a frequency greater than zero Hertz isconsidered to be an alternating current (AC) signal. A signal having afrequency approximately equal to zero is considered to be a directcurrent (DC) signal. An AC signal may oscillate about a “zero” amplitudelevel. A DC signal may be combined with the AC signal to generate an ACsignal with a “zero” offset approximately equal to the amplitude of theDC signal. In the example embodiment, a switch position signal indicatesa position of switch assembly 132 using only an AC signal component toindicate a first position or using an AC signal component and a DCsignal component to indicate a second position of switch assembly 132.In other embodiments, the signal components may be represented by otherelectrical characteristics that allow the position of switch assembly132 to be ascertained by controller 102. Method 200 also includessensing, by the controller, the position signal of the gas fuel valveswitch that includes only the first component when the gas fuel valveswitch is in a closed position, the gas fuel valve switch maintainingthe power supply leg and the power return leg closed when the gas fuelvalve switch is in the closed position. Method 200 further includesoperating 206 the gas fuel valve control system using the sensedposition of the gas fuel valve switch.

The foregoing detailed description illustrates embodiments of thedisclosure by way of example and not by way of limitation. It iscontemplated that the disclosure has general application to heatingdevices not incorporated into a water heater. It is further contemplatedthat the methods and systems described herein may be incorporated intoexisting heating devices, in addition to being maintained as a separatestand-alone method and system.

The logic flows depicted in the figures do not require the particularorder shown, or sequential order, to achieve desirable results. Inaddition, other steps may be provided, or steps may be eliminated, fromthe described flows, and other components may be added to, or removedfrom, the described systems. Accordingly, other embodiments are withinthe scope of the following claims.

It will be appreciated that the above embodiments that have beendescribed in particular detail are merely example or possibleembodiments, and that there are many other combinations, additions, oralternatives that may be included.

Also, the particular naming of the components, capitalization of terms,the attributes, data structures, or any other programming or structuralaspect is not mandatory or significant, and the mechanisms thatimplement the disclosure or its features may have different names,formats, or protocols. Further, the system may be implemented via acombination of hardware and software, as described, or entirely inhardware elements. Also, the particular division of functionalitybetween the various system components described herein is merely oneexample, and not mandatory; functions performed by a single systemcomponent may instead be performed by multiple components, and functionsperformed by multiple components may instead performed by a singlecomponent.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about” and “substantially”, are not to be limited tothe precise value specified. In at least some instances, theapproximating language may correspond to the precision of an instrumentfor measuring the value. Here and throughout the specification andclaims, range limitations may be combined and/or interchanged, suchranges are identified and include all the sub-ranges contained thereinunless context or language indicates otherwise.

This disclosure has been described in terms of example embodiments of anovel gas valve control system for heating devices. Various changes,modifications, and alterations in the teachings of the presentdisclosure may be contemplated by those skilled in the art withoutdeparting from the intended spirit and scope thereof. It is intendedthat the present disclosure encompass such changes and modifications.

The above-described embodiments of a method and system of operating agas fuel valve control system using the sensed position of the gas fuelvalve switch provides a cost-effective and reliable means fordeenergizing a gas fuel valve using both legs of a power supply to thegas fuel valve. The methods and systems described herein permit use of alighter duty gas fuel valve switch than at least some known powered ventheating systems are capable of using due to the gas fuel valve being theonly load switched in the present disclosure, as opposed to other knownsystems using the gas fuel valve switch to also switch, for example, alarge inductive fan load or an ignition circuit load. The methods andsystems described herein facilitate indicating to a heating devicecontroller the position of the gas fuel valve switch. In addition, theabove-described methods and systems facilitate maintaining the heatingdevice controller in an operational state while the gas fuel valveswitch is turned off. As a result, the method and systems describedfacilitate a cost-effective and reliable gas fuel valve control system.

This written description uses examples to describe the disclosure,including the best mode, and also to enable any person skilled in theart to practice the disclosure, including making and using any devicesor systems and performing any incorporated methods. The patentable scopeof the disclosure is defined by the claims, and may include otherexamples that occur to those skilled in the art. Such other examples areintended to be within the scope of the claims if they have structuralelements that do not differ from the literal language of the claims, orif they include equivalent structural elements with insubstantialdifferences from the literal languages of the claims.

What is claimed is:
 1. A gas valve control circuit of a water heatercomprising: a gas valve assembly configured to control a flow of a fuelgas to a water heater; and a switch assembly comprising a switch in eachleg of a plurality of legs of a power supply to the gas valve assembly,the switch assembly configured to supply power and a return to the gasvalve assembly in a first position and to open the plurality of legs ofthe power supply to the gas valve assembly in a second position, theswitch assembly configured to indicate a position of the switchassembly.
 2. The gas valve control circuit of claim 1, wherein theswitch assembly comprises a first double-throw switch configured tosupply power to the gas valve assembly in a first position and to injecta switch assembly position signal to a controller in a second position.3. The gas valve control circuit of claim 1, wherein the switch assemblycomprises a second double-throw switch configured to connect a returnpath to the gas valve assembly in a first position and to open thereturn path from the gas valve assembly in a second position.
 4. The gasvalve control circuit of claim 1, wherein the switch assembly comprisesa manually operated switch.
 5. The gas valve control circuit of claim 1,wherein the switch assembly is electrically coupled to the gas valveassembly through a bridge rectifier circuit.
 6. The gas valve controlcircuit of claim 1, further comprising a controller configured to sensea position of the switch assembly.
 7. The gas valve control circuit ofclaim 6, wherein the controller is configured to sense a gas valveposition signal having only an only an alternating current (AC)component when the switch assembly is in the first position.
 8. The gasvalve control circuit of claim 6, wherein the controller is configuredto sense a gas valve position signal having an AC component and a directcurrent (DC) component when the switch assembly is in the secondposition.
 9. A method of operating a gas fuel valve control system, saidmethod comprising: sensing, by a controller, a position signal of a gasfuel valve switch that includes a first component having a firstelectrical characteristic and a second component having a secondelectrical characteristic when the gas fuel valve switch is in an openposition, the second electrical characteristic being different than thefirst electrical characteristic, the gas fuel valve switch maintaining apower supply leg and a power return leg open when the gas fuel valveswitch is in the open position; and sensing, by the controller, theposition signal of the gas fuel valve switch that includes only thefirst component when the gas fuel valve switch is in a closed position,the gas fuel valve switch maintaining the power supply leg and the powerreturn leg closed when the gas fuel valve switch is in the closedposition; and operating the gas fuel valve control system using thesensed position of the gas fuel valve switch.
 10. The method of claim 9,wherein the first electrical characteristic is a frequencycharacteristic greater than approximately zero Hertz and the secondelectrical characteristic is a frequency characteristic equal toapproximately zero Hertz.
 11. The method of claim 9, wherein the firstelectrical characteristic and the second electrical characteristic arevoltage characteristics.
 12. The method of claim 9, further comprisingmanually positioning the gas fuel valve switch from one of the openposition and closed position to another of the open position and closedposition.
 13. A powered vent electronic control circuit comprising: acontroller configured to control an operation of heating device having apowered draft inducer; a gas valve assembly configured to control a flowof a fuel gas to a burner of a heating device; and a switch assemblycomprising a switch in each leg of a plurality of legs of a power supplyto the gas valve assembly, the switch assembly configured to supplypower and a return to the gas valve assembly in a first position and toopen the plurality of legs of the power supply to the gas valve assemblyin a second position, the switch assembly configured to indicate aposition of the switch assembly to the controller.
 14. The powered ventelectronic control circuit of claim 13, wherein the switch assemblycomprises a first double-throw switch configured to supply power to thegas valve assembly in a first position and to inject a switch assemblyposition signal to the controller in a second position.
 15. The poweredvent electronic control circuit of claim 13, wherein the switch assemblycomprises a second double-throw switch configured to connect a returnpath to the gas valve assembly in a first position and to open thereturn path from the gas valve assembly in a second position.
 16. Thepowered vent electronic control circuit of claim 13, wherein the switchassembly comprises a manually operated switch.
 17. The powered ventelectronic control circuit of claim 13, wherein the switch assembly iselectrically coupled to the gas valve assembly through a bridgerectifier circuit.
 18. The powered vent electronic control circuit ofclaim 13, further comprising a controller configured to sense a positionof the switch assembly.
 19. The powered vent electronic control circuitof claim 18, wherein the controller is configured to sense a gas valveposition signal having only an only an alternating current (AC)component when the switch assembly is in the first position.
 20. Thepowered vent electronic control circuit of claim 18, wherein thecontroller is configured to sense a gas valve position signal having anAC component and a direct current (DC) component when the switchassembly is in the first position.